The central objective of this project proposal is to further examine the regulation of primate prolactin secretion and synthesis with primary cultures of monkey pituitary cells maintained on extracellular matrix and in serum-free medium. Lactation, amenorrhea, and prolactin secretion, play a central role in the many different reproductive strategies that have evolved among mammalian species. To date, studies on the cellular regulation of prolactin secretion have utilized rat, bovine and ovine pituitaries because of availability, high cell yield and lower cost. However, results from studies on prolactin regulation in vivo with humans and monkeys are frequently inconsistent with the results from cellular studies with pituitaries from other species. Direct examination of prolactin regulation using primate pituitary cells has been minimal. Thus, the use of defined cultures of normal monkey pituitary cells in this proposal fills an important gap. Having established stable long-term serum-free cultures of monkey pituitary cells on extracellular matrix, and having characterized the effects of estrogen and dopamine in these cultures as compared to the pituitary stalk-transected monkey, future experiments will focus on the direct effects of progesterone and prolactin-releasing peptides and their possible interaction with estrogen and dopamine on prolactin secretion and synthesis in cultures of monkey pituitary cells. The results will be compared to studies conducted in vivo with monkeys which have pituitary stalk-transections. In addition, the establishment of a nonhuman primate model for hyperprolactinemic amenorrhea will be pursued using peripheral pituitary allografts and/or pituitary cell injections in combination with the immune suppressor, Cyclosporin A. Definition and investigation of a clustering phenomena exhibited by monkey pituitary hormone-producing cells in culture will also be undertaken. Collaborations include production of a monoclonal antibody to the undifferentiated cell types in monkey pituitary cultures, transformation of monkey pituitary hormone-producing cells into growing cells, production of monoclonal antibodies to monkey pituitary hormones and purification of monkey prolactin from serum-free culture medium.